Dr. Mackenzie is now a plastic surgeon, but he formerly worked in the immunology division of the military overseeing vaccines. He was originally pro-vaccine because he had no idea that there were any physicians who questioned vaccines, not because he actually researched the matter.
As he began to prepare to become a father, he decided to research vaccines further. He states in the interview that he had "no ax to grind" and "no skin in the game," and was therefore just looking for the truth.
He read books by Dr. Andrew Wakefield and Dr. Suzanne Humphries that questioned vaccines, as well as books that promoted vaccines, particularly by Dr. Paul Offit.
Dr. Mackenzie states:
"Any physician who will do their own research, and look at the science, both sides of this, and look where the biases are, and look at the bad epidemiology that is out there, will have a change of heart. That's assuming they don't have a lot at stake."